Reproductive behavior in Drosophila will be examined, using genetic variants. Mutations that alter circadian rhythms also influence short-term oscillations in acoustical features of the courtship song. We will analyze the neural control of these oscillations in part by measuring them in males expressing physiological mutations. We will assess the adaptive significance of the fluctations, using a "simulator" device that can play song-like vibrations; with and without the oscillations, to courting flies. Mutations affecting conditioned behavior also influence certain features of courtship. We will analyze these effects further, with respect to possible affect-effects of simulated, oscillating song played to flies that express the learning mutations. Mosaics with part-mutant, part normal nezvous systems have provided much information on the neural control of Drosophila reproductive behavior. We will use these mosaics further, in order to determine neural sites--affected by a song rhythm mutation, or physiological mutations--that control the oscillations of the song. Mating behavior per se will be further analyzed, using a new mutant that has found to have lengthened copulation and using the rhythm mutations which have been found to affect this timing phenomenoa as well as those noted above. Olfactory cues have been found to exert important influences on courtship. We will study the relevant pheromones and the genetic control of their production, by spectrographic analysis of volatile compounds that are particularly associate with sexually attractive flies of various genotypes. We will also make physiological recordings from putative olfactory receptors on various appendages, to determine which ones are responsible for the initial reception of these olfactory cues.